Mobile IP (Internet Protocol) (for example, RFC3344.txt (C. Perkins, Ed., “IP Mobility Support for IPv4”, August 2002), RFC3775.txt (D. Johnson et al., “Mobility Support in IPv6”, June 2004)) is known as one of the key technologies for performing seamless communication on the Internet.
FIG. 8 is a diagram showing an example of the construction of a network system based on Mobile IPv6 and an example of the operation thereof. The network system 2 has Mobile Node (MN) 800, a Correspondent Node (CN) 200 as a communication peer node of the Mobile Node (MN) 800, first and second Access Routers (AR#1, AR#2) 300, 400, an AAA server (Authentication, Authorization, and Accounting Server) 500 for performing authentication, etc. of the Mobile Node (MN) 800, Home Agent (HA) 600 as a movement managing agent of the Mobile Node (MN) 800 and an IP network 700.
The network work system 2 described above operates as follows. When the Mobile Node (MN) 800 moves from a cell under a first Access Router (AR#1) 300 to a cell under a second Access Router (AR#2) 400, the Mobile Node (MN) 800 obtains a Care-of Address from the Access Router (AR#2) 400. The Mobile Node (MN) 800 transmits a registration message (Binding Update) containing a Care-of Address (CoA#2) to a Home Agent (HA) 600. The Home Agent (HA) 600 stores the Home Address (HoA) of the Mobile Node (MN) 800 and the Care-of Address (CoA#2) into a binding cache 610 in the Home Agent (HA), and holds them for a fixed time.
Thereafter, the Correspondent Node (CN) 200 generates a data packet and transmits it to the Mobile Node (MN) 800. At this time, the transmission source address of the data packet is the address (“CN”) of the Correspondent Node (CN) 200 and the Home Address (“HoA”) of the Mobile Node (MN) 800.
The Home Agent (HA) 600 intercepts this packet and refers to the binding cache 610. Then, the Home Agent (HA) 600 encapsulates and transmits the packet. The transmission source address of the encapsulated packet is set to the address (“HA”) of the Home Agent (HA) 600, and the destination address thereof is set to the Care-of-Access (“CoA#2”) of the Mobile Node (MN) 800.
The Mobile Node (MN) takes out the data portion of the encapsulated packet to decapsulate the data and restores the packet transmitted from the Home Agent (HA) 600 to the data packet transmitted from the Correspondent Node (CN) 200.
In general, an IP application identifies a session from the pair of the transmission source and destination of the packet. With respect to the application of the Mobile Node (MN) 800, even when the Care-of Address is changed, the pair of addresses of the transmission source and the transmission destination of the packet transmitted from the Correspondent Node (CN) 200 (the address (“CN”) of the Correspondent Node 200), and the Home Address (“HoA”) of the Mobile Node (MN) 800 are not varied before and after the movement. Therefore, communications can continue even when the Mobile Terminal (MN) 800 is handed over.
However, Mobile IPv6 requests a protocol inherent to the mobile node, for example, the transmitting function of the registration message (Binding Update), etc. to the Mobile Node (MN) 800. Accordingly, a Mobile Node (MN) 800 which does not have the transmitting function concerned cannot utilize the Mobile IP service. Therefore, for the purpose of supplying a service equivalent to Mobile IP to a Mobile Node in which Mobile IP is not mounted as an IP stack (a function of performing communications by using IP), Proxy Mobile IPv6 has been proposed (for example, draft-ietf-netlmm-proxymip6-01.txt (S. Gundavelli et al., “Proxy Mobile IPv6”, Jun. 18, 2007).
FIG. 9 is a diagram showing an example of the construction of a network system 3 based on Proxy Mobile IPv6 and an example of the operation thereof. In Proxy Mobile IPv6, a nearest router (defined as MAG (Mobile Access Gateway) in “Proxy Mobile IPv6”) 450 transmits a registration message to a Home Agent (defined as LMA (Local Mobility Anchor) in “Proxy Mobile IPv6”) in place of the Mobile Node (MN) 800, whereby Proxy Mobile IPv6 can continuously perform communications even when Mobile IPv6 is not mounted in the Mobile Node 800 (for example, the function of transmitting the registration message) is not mounted.
That is, when the second router (MAG#2) 450 detects that the Mobile Node 800 moves to the control thereof, the second router (MAG#2) 450 transmits the registration message (Proxy Binding Update message) to the Home Agent (LMA) 650. The Mobile Node (MN) 800 performs communications by using a specific IP address, for example, a fixed address (HoA (Home Address)). This registration message contains the fixed address (HoA). When receiving the registration message, the Home Agent (LMA) 650 stores the pair of the IP address of the Mobile Node (MN) 800 (for example, “HoA”) and the address of the router (MAG#2) 450 (for example, “MAG#2”) into the binding cache 620, and holds them for a fixed time.
When a packet is transmitted from the Correspondent Node (CN) 200 of the communication peer MN 800, the Home Agent (LMA) 650 intercepts this packet, and refers to the binding cache 620 to encapsulate the packet. The transmission source address of the encapsulated packet is the Home Agent (LMA) 650, and the destination address is the second router (MAG#2) 450. When receiving this packet, the second router (MAG#2) 450 decapsulates the packet, takes out the packet inserted in the data portion and then transmits the taken-out packet to the Mobile Node (MN) 800 under the control thereof. The transmission source address of this packet is the address of the Correspondent Node (CN) 200, and the destination address thereof is the IP address of the Mobile Node 800, and these addresses are identical to the addresses of the transmission source and the destination of the packet transmitted from the Correspondent Node (CN) 200. Accordingly, even when the Mobile Node (MN) moves, the communication can be continued.
A Mobile Node such as a mobile PC (Personal Computer), a cellular phone or the like can enjoy plural wireless accesses using a communication device based on external equipment such as a PC card or the like or various kinds of built-in communication devices. However, the IP address used for communications is different for every communication device or for different built-in communication devices. This is because a company for managing and issuing an IP address may change for every communication device.
On the other hand, in the above-described Proxy Mobile IP, when the communication device is changed based on the type of communication (for example, changed from wireless LAN to a cellular or the like), the Mobile Node changes the IP address used for the communication and then performs communications.
FIG. 10 is a diagram showing an example of the operation when the communication device is changed. As shown in FIG. 10, the Mobile Node (MN) 800 performs communications by using a first interface (INF#1) 810 under the control of the first router (MAG#1) 350. Thereafter, the Mobile Node (MN) 800 moves to a cell under the second router (MAG#2) 450, changes the communication device and performs communications by using a second interface (INF#2) 820. At this time, the Mobile Node (MN) 800 performs communications by using an IP address (“b1”) which is different from an IP address (“a1”) used under the control of the first router (MAG#1) 350.
When the IP address is changed during communication, in Proxy Mobile IP, the Mobile Node (MN) 800 executes the procedure of disconnecting a call (call release) of a route used before the communication device is changed and re-connecting a call after the communication device is changed (call re-connection).
However, the execution of the call release and the call re-connection by the Mobile Node (MN) 800 has a problem that a long service interruption may result when the communication device is switched.
Therefore, it is desirable to provide a network system in which a service interruption time is shortened, a data transmitting/receiving method in the network system and a data transmission/reception program.